Due to rising fuel prices and concerns about future fuel availability, many have sought to increase the efficiency of engines. Desirably, by increasing engine efficiency, less fuel is consumed, and the cost of fueling internal combustion engines is decreased.
A large quantity of moderate-to-high temperature heat is rejected by an engine. Exhaust gases leave the engine at a high temperature, and heat escaping through the working chamber boundaries, and/or due to friction, may be collected at an elevated engine block temperature. Pressurized and superheated, dry steam is generated with heat that is rejected by the engine. This steam is admitted into the same working chamber, in which the fuel is also burned. Additional work is pneumatically recovered from the steam, thus augmenting the total work obtained by the engine.
U.S. Pat. Nos. 1,676,264; 2,919,540; 3,995,421 and 4,122,803 disclose steam-augmented engines, in which a substantial portion of the steam is admitted into the working chamber during or after combustion of the fuel, that is, after ignition of the fuel.
U.S. Pat. Nos. 1,088,292; 4,402,182; and 4,409,932 and disclose steam-augmented engines, in which all of the steam is admitted into the working chamber, within the “power stroke”. No further description is given for admitting the steam before ignition of the fuel.
U.S. Pat. No. 4,637,352 discloses a steam-augmented piston engine, in which steam is admitted into the working chamber, either at the very end of the “compression stroke” or at the very beginning of the “power stroke”, both at exactly top center. No further description is given for admitting the steam before ignition of the fuel.
U.S. Pat. No. 6,463,890 discloses an engine that either admits steam into the working chamber after ignition of the fuel, or into a region separate from the fuel, or both, and thus does not form a substantially homogeneous ternary mixture comprising a majority of the steam, a majority of the air, and a majority of the fuel before ignition of the fuel.
U.S. Pat. No. 6,170,441 discloses an engine admitting a supercritical mixture of fuel and steam into the working chamber near the end of compression or near top center. No further description is given for admitting at least a majority of the steam and at least a majority of the fuel into the working chamber before ignition of the fuel.
U.S. Pat. No. 3,842,808 discloses a steam-augmented engine, wherein the fuel is drafted into the working chamber, and superheated steam is admitted into the working chamber at a steam admission temperature that is controlled or chosen such that the steam ignites the fuel. An early portion of the steam appears to ignite the fuel before the remaining late portion of the steam can be admitted into the working chamber. Admission of at least a majority of the steam into the working chamber, before ignition of the fuel, is not shown.
Japanese Patent JP4648466, has issued from Japanese Patent Application No. JP2009168039, which was also published as U.S. Patent Publication No. 2004/0003781. U.S. Patent Publication No. 2003/0188700 was also published on a similar invention which appears to be from the same line of effort. These reports relate to steam-augmented engines using direct injected and compression ignited fuel. In all embodiments disclosed in U.S. Patent Publication No. 2004/0003781, the direct injected fuel is autoignited by contacting of the fuel by the air and/or steam. An early portion of the fuel appears to ignite before the remaining late portion of the fuel can be admitted into the working chamber. Admission of a majority of the fuel into the working chamber, before ignition of the fuel, is not shown.
The well-known method, for preventing knock, comprises direct injection of a fuel and heterogeneous combustion substantially within the fuel injection interval, such that the combustion rate is limited by the rate of fuel injection. In such a combustion mode, a late, major portion of the fuel is admitted into the working chamber after ignition of an early, minor portion of the fuel. However, a large convective heat loss occurs if a gaseous fuel is combusted in this manner. This large convective heat loss explains the 10 percent fuel economy loss that is experienced in operation of direct injected, methane fueled engines that admit most of the methane into the working chamber after ignition of the fuel, as compared to otherwise similar engines combusting only liquid diesel oil. This fuel economy difference is disclosed in “Norcal Prototype LNG Truck Fleet: Final Results”, authored by Kevin Chandler and Ken Proc in July 2004. A hydrogen fueled engine suffers an even larger efficiency loss than does a methane fueled engine if operated in this manner, because hydrogen displaces about 3.3 times more volume than does methane, for the same quantity of energy.
Gaseous fuels such as hydrogen are listed among the possible fuels that can be used in the invention disclosed in U.S. Patent Publication No. 2004/0003781. However, the drawings and description appear to be directed to the use of a direct injected liquid fuel that is autoignited, and the majority of the fuel appears to be admitted into the working chamber after ignition of an early, minor portion of the fuel. The invention in U.S. Patent Publication No. 2004/0003781 would not have suffered a large convective heat loss when using a liquid fuel in the manner described, because liquid fuels displace a much smaller volume than do gaseous fuels, at a broad range of pressures and for the same quantity of energy. The inventors in U.S. Patent Publication No. 2004/0003781 appear not to have anticipated the necessity of admitting at least a majority of a direct injected gaseous fuel into the working chamber before ignition of the fuel.
Based on the foregoing, there is a need for a steam-augmented spark ignition engine, wherein a yet-to-be-burned ternary mixture comprising fuel, oxidizer, and steam is formed under compression. The ternary mixture is combusted upon ignition of the fuel by an igniter. The steam is admitted into the working chamber of the engine within the final one third of the compression time interval and before the ignition of the fuel. Both the fuel and the oxidizer are flowed into the working chamber before the ignition of the fuel.